In recent years, the studies of an organic thin-film light emitting device (LED: light emitting device) have actively been conducted such that an electron injected from a cathode and a hole injected from an anode emit light when recombining in an organic fluorescent compound held between both of the cathode and the anode. This emitting device is characterized by thin type, high brightness under low driving voltages and multicolor light emission through selection of light-emitting materials, thereby attracting notice.
These studies have been conducted by many research institutions since it was revealed by C. W. Tang et al. of Eastman Kodak Company that an organic thin-film device emitted light with high brightness. The typical structure of an organic thin-film emitting device presented by a study group of the Kodak Company is such that a diamine compound for hole transporting, tris(8-quinolinolate)aluminum (III) as a luminescent layer and Mg:Ag (alloy) as a cathode are sequentially layered on an ITO glass substrate, which emitting device allows green light emission of 1000 cd/m2 at a driving voltage of approximately 10 V (refer to Nonpatent Document 1).
The use of various fluorescent materials for a luminescent layer allows an organic thin-film emitting device to obtain diverse luminescent colors, so that the studies of practical application to displays are active. Among light-emitting materials of the three primary colors, the studies of green light-emitting materials are the most advanced, and the earnest studies in red light-emitting materials and blue light-emitting materials are presently made toward performance improvement.
One of the largest problems in an organic thin-film light emitting device is to improve durability of the device. In particular, with regard to a blue light emitting device, few blue light-emitting materials provide a device having excellent durability and high reliability. For example, a technique is disclosed in which an anthracene compound is used for a blue light emitting device light emitting device. Blue light emitting devices using various anthracene compounds (refer to Patent Documents 1 to 6) are reported; however, any of them has insufficient durability.    Non-patent Document 1: Applied Physics Letters (USA) 1987, Vol. 51, No. 12, pp 913 to 915    Patent Document 1: Japanese Unexamined Patent Publication No. 11-297473 (Claims)    Patent Document 2: Japanese Unexamined Patent Publication No. 2000-273056 (Claims)    Patent Document 3: Japanese Unexamined Patent Publication No. 2002-260861 (claim 4)    Patent Document 4: Japanese Unexamined Patent Publication No. 2003-128651 (Claims)    Patent Document 5: Japanese Unexamined Patent Publication No. 2003-306454 (claim 1, paragraph 0039)    Patent Document 6:Japanese Unexamined Patent Publication No. 2004-2351 (claim 1, paragraphs 0049 to 0050)